De reparatie van Bally Electronische Flipperkasten uit de periode 1977 tot 1985
Deze pagina is tot stand gekomen door het aanleveren van technische informatie van duizenden flipperkastliefhebbers en techneuten over de hele wereld.
Oorspronkelijk stonden deze pagina's in het Engels op pinrepair.com maar na de totale geestelijke instorting van Clay Harrel in 2011 zijn deze offline gehaald.
Wij zullen deze pagina's op termijn allemaal in het Nederlands vertalen.

U vindt hier hulp bij de reparatie van elektronische Bally flipperkasten die gebouwd werden van 1977 tot 1985
Omdat de firma Stern flipperkast bouwde met bijna identieke electronika worden ook deze hier besproken.

BELANGRIJK:
Als je geen ervaring hebt in het repareren van printplaten, dus een goede vaardigheid in solderen hebt kun je dit beter niet zelf proberen.

De meeste professionele reparateurs nemen GEEN printplaten aan die door eerdere reparatiepogingen vernield werden (gehacked)
Je kunt soldeerwerk en printplaatreparatie in zo'n geval het beste door gespecialiseerde reparateur zoals de Flipperwinkel in Arnhem laten uitvoeren. 

Speciale dank aan Leon Borré voor het schrijven van testsoftware waarmee het opsporen van fouten flink vereenvoudigd is.

Table of Contents

1. Getting Started:
1. Experience, Schematics, Manuals
2. Necessary Tools
3. Parts to have On-Hand
4. Game List
5. Lubrication Notes
6. The Circuit Boards
7. Voltage Test Points on the Boards
8. Power Supply Power Distribution

2. Before Turning the Game On:

1. Removing the MPU Battery and Fixing Corrosion
2. Rebuilding the Power Supply
3. Upgrading the Voltage Regulator/Solenoid Driver Board
4. Upgrading the Ground on the MPU Board
5. Ok, So You Didn't Do the Above. You BETTER do This!
6. Connectors
7. Setting Free Play

3. When Things Don't Work:

1. Making a MPU test fixture
2. Fixing the MPU (LED flashes and the such)
3. Game ROMs, EPROMs, and Jumper - the Basics
4. -35 MPU Game ROMs, EPROMs, and Jumpers
5. -17 MPU Game ROMs, EPROMs, and Jumpers
6. Stern M-200 MPU Jumpers (using a Stern M-200 in a Bally Game)
7. Converting a -133 MPU (Baby Pacman) to a -35 MPU
8. The Built-In Diagnostics/Bookkeeping
9. Locked-on or Not Working Coils (Solenoid Driver board)
10. Locked-on or Not Working Feature Lights (Lamp Driver board)
11. Solenoid Expander Board Problems
12. Auxiliary Lamp Driver Board Problems
13. Switches and the Switch Matrix
14. High Voltage Section Problems
15. Score Display Replacement and Fixes
16. Sound Board Problems
17. Miscellaneous Problems and Fixes

Bibliography.
In the creation of this document, some information came from the following sources:

• Tom Callahan web articles. Available at www.repairconnection.com.
• "Electronic Pinball Games Repair Procedures", Bally, part number F.O.560-3, fourth edition, dated October 1, 1981. Available from the Pinball Resource, 845-473-7114 or PBResource@idsi.net.
• Pinball Lizard Tech Reprint articles, J. Cook, 1995, 1996. Available from www.pbliz.com.

Left: U9 (CPU) pin 5, and U19 pin 8 look like this.	Right: U19 pin 10, and U14 pin 11 look like this.

Left: U14 pin 12, and U15 pin 4 look like this.	Right: U15 pin 5.

Left: U15 pin 6, and U15 pins 1 and 2 look like this.	Right: U15 pin 3.

• Check U9 (CPU) address and data lines with your logic probe for pulsing signals. This includes pins 9 to 22, 24 (address lines, pin 24 is only used if 2732 EPROMs installed) and pins 26 to 33 (data lines).
• If the PIA at U11 is bad (or its socket is bad), all the above pulses can be present and acting correctly. Yet the LED will still be stuck on. This PIA is right in the "corrosion zone", so make sure the U11 socket and chip are in good shape.
• If C23 on the solenoid driver board is not filtering the +5 volts effectively, this can cause the MPU to lock and leave the LED on (see Upgrading the Voltage Regulator/Solenoid Driver Board for details on this).
• If Q20 (the +5 voltage regulator) on the Solenoid Driver board is bad, the LED will remain on.

If you've gotten to this point, and the MPU's LED is still staying lit, you may want to consider sending the board out for repair.

Strengthen the Reset Signal by Replacing Caps C14 and C15.
The two capacitors at C14 and C15 (470 pfd) should also be replaced. If these capacitors are weak, the reset signal will not be as crisp and strong. This is very apparent if you have a scope.

Was there Work Done on Chips U15 and U16?
If chips U15 or U16 were worked on, suspect problems. Even though these chips are not directly involved in the reset circuit, there are very fragile traces which travel underneath the U15/U16 sockets. If someone replaced these chip and/or sockets, these traces could be damaged. Using a ohm meter and check for continuity on all of these traces (this may require removing the U15/U16 sockets; always replace these sockets with strip socket headers, so the traces maybe seen and worked on easily in the future).

More on the RESET Signal and a Locked-on LED.
A major part of the reset circuit is transistor Q1, and there is an easy way to test it. As we learned above, when the game is first turned on, the reset line (pin 40 of the U9 CPU) goes low for just a moment, then sticks high. You can similate a reset by shorting the ground junction of resistors R1 and R3. This will force a reset in a good MPU board. As you do this, watch pin 40 of U9 with your logic probe. It should go low for a moment, then stick high. If it doesn't, try replacing Q1 (2N3904). If Q1's collector doesn't go to about 4 volts DC when R1/R3 junction is grounded, then Q1 is bad.

Q5 gets Cooked by R11, and the Game Re-boots Intermittently.
Another strange problem relates to transistor Q5 (2N4403). This transistor is also part of the reset circuit (along with Q1), and is located right below R11, an 82 ohm 2 watt power resistor. The problem here is resistor R11 gets HOT, and is sometimes touching Q5. The heat is transfered to Q5, and this can cause the MPU board to suddenly stop running, and reboot the game. To fix this, provide an air gap between Q5 and R11. You should also probably replace Q5 too. If you replace R11, make sure you leave some "air" between R11 and the MPU board.

The Game only Starts up "sometimes".
If the MPU only starts up properely "sometimes", replace Q1 and Q2 (both 2N3904), Q5 (2N4403), VR1 (1N959B or 1N4738A) and CR5 (1N4148 or 1N914). These transistors and diodes need to be in perfect working order for the MPU to boot reliably.

LED Still Locked On: MPU Board Signals.
If having play problems with an otherwise working MPU, check all the chip's signals with a logic probe, and cross reference them to this chart. If a signal is other than shown below, check the schematic. If it's an input line to the chip, the device that feeds that pin is probably bad. If it's an output line from the chip, the chip itself is probably bad.

All the following signals are with the MPU board in "attract" mode, and a MPU -35 loaded with Kiss 2732 EPROM's at U2 and U6. Because these signals are with the game in attract mode, this chart won't help much if your MPU is in some other state.
Key:

• H = Logic High (+5)
• L = Logic Low (GND)
• P = Pulse
• HP = High Pulse (signal is mostly high but pulsing)
• LP = High Pulse (signal is mostly low but pulsing)
• X = No signal

Chip	Pin/Signal				Chip	Pin/Signal
U16 (9602)	L 1		16 H		U15 (MC3459)	P 1		14 H
	LP 2		15 L			P 2		13 P
	H 3		14 LP			P 3		12 P
	P 4		13 H			P 4		11 P
	H 5		12 P			P 5		10 P
	P 6		11 H			P 6		9 P
	P 7		10 P			L 7		8 P
	L 8		9 P

Chip	Pin/Signal				Chip	Pin/Signal
U20 (4502)	P 1		16 H		U17 (7400)	P 1		14 H
	P 2		15 L			P 2		13 P
	P 3		14 P			P 3		12 P
	L 4		13 HP			P 4		11 P
	LP 5		12 HP			P 5		10 P
	P 6		11 LP			P 6		9 P
	LP 7		10 P			L 7		8 HP
	L 8		9 LP

Chip	Pin/Signal				Chip	Pin/Signal
U18 (4049)	H 1		16 X		U19 (4011)	HP 1		14 H
	P 2		15 P			HP 2		13 P
	P 3		14 P			P 3		12 P
	P 4		13 X			P 4		11 P
	P 5		12 P			H 5		10 P
	P 6		11 P			HP 6		9 H
	HP 7		10 H			L 7		8 P
	L 8		9 L

Chip	Pin/Signal				Chip	Pin/Signal
U14 (4049)	H 1		16 X		U12 (555)	L 1		8 H
	P 2		15 LP			HP 2		7 P
	P 3		14 HP			HP 3		6 P
	P 4		13 X			H 4		5 H
	HP 5		12 P
	HP 6		11 P
	P 7		10 HP
	L 8		9 P

Chip	Pin/Signal				Chip	Pin/Signal
U2 (ROM)	P 1		24 H		U6 (ROM)	P 1		24 H
	P 2		23 P			P 2		23 P
	P 3		22 P			P 3		22 P
	P 4		21 P			P 4		21 P
	P 5		20 P			P 5		20 P
	P 6		19 P			P 6		19 P
	P 7		18 L			P 7		18 P
	P 8		17 P			P 8		17 P
	P 9		16 P			P 9		16 P
	P 10		15 P			P 10		15 P
	P 11		14 P			P 11		14 P
	L 12		13 P			L 12		13 P

Chip	Pin/Signal				Chip	Pin/Signal
U7 (6810)	L 1		24 H		U8 (5101)	P 1		22 H
	P 2		23 P			P 2		21 P
	P 3		22 P			P 3		20 P
	P 4		21 P			P 4		19 P
	P 5		20 P			X 5		18 P
	X 6		19 P			P 6		17 H
	P 7		18 P			P 7		16 P
	P 8		17 P			L 8		15 P
	P 9		16 P			P 9		14 P
	P 10		15 P			P 10		13 P
	P 11		14 P			P 11		12 P
	P 12		13 P

Chip	Pin/Signal				Chip	Pin/Signal
U10 (6820)	L 1		40 H		U11 (6820)	L 1		40 HP
	P 2		39 HP			HP 2		39 LP
	P 3		38 HP			H 3		38 HP
	P 4		37 HP			P 4		37 HP
	HP 5		36 P			P 5		36 P
	P 6		35 P			P 6		35 P
	P 7		34 H			P 7		34 H
	P 8		33 P			P 8		33 P
	P 9		32 P			P 9		32 P
	HP 10		31 P			H 10		31 P
	HP 11		30 P			H 11		30 P
	HP 12		29 P			H 12		29 P
	HP 13		28 P			H 13		28 P
	HP 14		27 P			H 14		27 P
	HP 15		26 P			L 15		26 P
	HP 16		25 P			H 16		25 P
	HP 17		24 P			H 17		24 P
	LP 18		23 P			L 18		23 P
	LP 19		22 P			H 19		22 P
	H 20		21 P			H 20		21 P

Chip	Pin/Signal
U9 (6800)	L 1		40 H
	H 2		39 L
	P 3		38 L
	HP 4		37 P
	P 5		36 P
	H 6		35 L
	L 7		34 P
	H 8		33 P
	P 9		32 P
	P 10		31 P
	P 11		30 P
	P 12		29 P
	P 13		28 P
	P 14		27 P
	P 15		26 P
	P 16		25 LP
	P 17		24 P
	P 18		23 LP
	P 19		22 P
	P 20		21 L

The LED is Always OFF, and Never Comes On.
This can be caused by a lack of +12 volts getting to the LED, or the LED could be dead. A dead LED happens quite a bit actually. But first trace the +12 volts:
• TP2: should have +12 volts.
• R29: should have +12 volts on both sides of this 1/2 watt 470 ohm resistor.
• Q2: should have +11 volts on the leg closest to U11 (PIA). <-- CLAY CHECK THIS.
• Q2: Cross the two legs that are next to each other with a screw driver. The LED should come on.

If +12 volts is at the above three points (or at least two of them), the LED is probably bad. If you have the above voltages, cross the two adjacent legs of Q2 together with a screw driver. This should light the LED. If it doesn't, and the above voltages exist, replace the LED.

Ok, the MPU's LED "Flickers": What's Next?.
At this point you have an "unlocked" MPU board. By "unlocked" I mean you get the intial LED flicker upon power-on. This tells us that U6, U9 and U11 are good, and the CPU is "running". Now the MPU will test the other components on the board. So at this point, you should have all the other socketed chips like U7, U8, U10, U2, etc (if you removed them) back in the board. The U6 ROM will continue to run its diagnostics on the other components on the MPU board and will FLASH when each of its tests are COMPLETED. What follows is a description of these flashes (or lack of them), and what they mean.

The MPU Diagnostic LED Flash Sequences Explained.
1st Brief Flicker:
The Fakers Guide: If the LED briefly flickers on power-up, U6 (ROM), U9 (CPU), U11 (PIA), the reset components, and +5 volts DC are good (remember some Stern games also require the U2 and/or U5/U6 ROMs for the first flicker). If the LED locks on, one of these components (or some other supporting components such as the MPU's Q1, Q2, Q5, VR1, or C23, Q20 on the solenoid driver board) are bad (see above). Also the traces connecting these components together could be bad (battery corrosion!).

Techno Guide: On power-up, the U9 CPU chip requires +5 volts DC be applied before the reset line is allowed to swing from 0 to +4.8 volts. It also requires the presense of a two-phase, non-overlapping clock pulse. If these conditions are met, and if the U9 CPU chip itself is good, the LED on the MPU board briefly flickers.

The brief flicker indicates the operation is proper. The MPU has gone out to memory and obtained the starting address of the self-test from memory. The flicker indicates that it then went to that address and started to execute the self-test program.

The Valid Power Detectors circuit on the U9 CPU works with the +5 volts DC regulator Q20 on the solenoid driver board. This prevents the reset line from going high until +5 volts DC is proper at the U9 CPU chip. Q20 is supposed to go into regulation when +7.5 volts DC is applied to its input. This means that when the game is turned on, and a sufficient time (milliseconds) has passed so that C23 on the solenoid driver board has charged, Q20 switches into regulation. This supplies +5 volts DC to the MPU board.

Q1 on the MPU board (in the valid power detector circuit) does not allow the CPU chip to turn on immediately. The zener diode VR1, in series with the base of Q1 delays application of the reset voltage until C23 charges. At this point, Q1 and Q5 on the MPU board go into conduction, and the reset line at the MPU is caused to go high. Only then is the U9 CPU chip "on".

The importance of the Valid Power Detection circuit can be appreciated when the following fact is known; should the reset line be allowed to go high before the +5 volts is applied and proper, or should the +5 volt supply fail and go out of regulation, the U9 CPU chip can jump out of the program. The reason this happens is that the U9 CPU goes out to the program memory bank U1-U6 for instructions. The logic levels are wrong because the +5 volts is not proper. The MPU misinterprets the data, jumps out of the program, and executes this misinterpreted program! The U9 CPU is now like a train that has left the tracks, and it can end up anywhere. The difference is that a train will eventually stop. But the U9 CPU may continue as long as the clock circuit continues to run.

If the U9 CPU jumps out of the program, it is said to be in "run away". While it is mis-interpreting the program, it invariably overwrites the Bookkeeping function in U8 and the scratch pad RAM. An indication of a "run away" would be false data in bookkeeping. Probable cause is a faulty Q20 or C23 (or both) on the solenoid driver boared, or a leaky zener diode VR1 on the MPU board.

First Flash:
The Fakers Guide: No first flash means one of the game program ROMs U1 to U6 is bad. Could be a mis-jumpered board, or a bad ROM chip at U1 to U6.

Techno Guide: the U9 CPU chip next goes out to the program ROM's (read only memory) U1 to U6. It tests each chip in the bank, in accordance to how the MPU board is jumpered. When it finds the bank is correct, it flashes the LED for the first flash. A fault in the U1 to U6 ROM chips is indicated by the absense of the first flash.

The U9 CPU tests each ROM chip's function like this: in a game with ROM chips U2 and U6 (typical), the CPU first goes to U2. It fetches the first byte in U2, and adds it to the second byte in U2. It will add to this sum the third byte in U2. This continues until all bytes in the chip have been added up. If the sum of all the bytes is "0000 0000", the U9 CPU proceeds to U6 and repeats this process. If U6 has a sum of "0000 0000", the U9 CPU causes the LED to flash the first time. Fault in either U2 or U6 is indicated by the absence of the first flash.

The contents of each ROM chip have byte locations called checksums, reserved for this test routine. There is one checksum byte reserved in each 512 bytes of ROM memory. The game programmer at Bally must insert a btye with the proper value in each checksum byte location to force each 512 byte checksum to equal "0000 0000".

During the life of an electronic game, if a ROM chip U1 to U6 fails by so much as a single bit, it will be detected during this CPU test. The CPU will not continue until the defective ROM chip is replaced.

Second Flash:
The Fakers Guide: no second flash means U7 (6810) is bad.

Techno Guide: The U9 CPU chip goes out to the U7 RAM and erases the contents of the first byte (U7 is a 128 byte scratch pad memory). It then tries to read back the word "0000 0000" (indicating erased). If it can read it back, it adds "1" and continues. 256 tries later, it writes the word "1111 1111". If it can read it back, it has determined that the first byte in U7 is good. It repeats this process for each of the 128 bytes of RAM in U7, one at a time. If at the end of this 256 x 128 (=32,768) tests, each time the CPU writes, it can read the same word back, the CPU cause the LED to flash a second time.

Note the pause between the first and second flashes. This is the CPU doing 32,768 tests to the RAM at U7 and repeats the process.

Third Flash:
The Fakers Guide: no third flash means U8 (5101) is bad.

Techno Guide: The U9 CPU goes out to U8 (CMOS 5101 RAM) and makes a copy of the contents of the first half byte. It does this because U8 is battery supplied, non-volatile memory where the bookkeeping functions are stored. It then erases the contents of the first half byte, and tries to read back the word "0000 xxxx". If it can read it back, it adds "1" to the previous word (giving "0001 xxxx"). It continues to write and read until it reaches the word "1111 xxxx". When this is done successfully, the CPU restores the original contents to the first byte located in U8. It then makes a copy of the contents of the second byte, and repeats the process. It does this for the entire 256 bytes, one at a time. If at the end of the 256 x 16 (=4096) test, each time the CPU writes and reads the same word correctly, the CPU caused the LED to flash a third time.

Fourth Flash:
The Fakers Guide: no fourth flash means U10 (6821 PIA) is bad.

Techno Guide: The U9 CPU chip now tests the first 6821 PIA chip. There are two of these chips on the MPU board, which are identical and interchangable. The test for both is the same.

To determine if a PIA chip is good, the U9 CPU does the following:

1. The CPU accesses, by means of input RS0, RS1, CS0, CS1 and CS2 each of the two full byte registers used to store the port initialization information. If does this, one register at a time. After it completes the first register, it repeats for the second. It goes through 256 tests similar to that used to check each byte in U7 (second flash). If each time the CPU writes a word into the register, it can read the same word back, it continues to test until completion.
2. The CPU accesses, by means of input RS0, RS1, CS0, CS1 and CS2, each of two full byte registers used as data output registers when PA0 to PA7 and PB0 to PB7 are used as outputs. It does the same type of test on each register as described just above. Again if no faults are found, the test is continued until completion.
3. The CPU then accesses, by means of input RS0, RS1, CS0, CS1 and CS2, the two ports CA2 and CB2. The port is initialized as an output. The port is then written into to see if it can store a "1" and then a "0".
A total of 4 x 256 + 4 (=1028) test steps are required to test the PIA chip. However, there are internal buffer amplifiers used with the PB0 to PB7 output registers and CB2 port register which can not be tested by the CPU. Access is only to the register; if the buffer is open, it does not interfere with the registers ability to be written into and read from by the CPU. It is this uncertainity that reduces the accuracy of these test to 99.5%.

Fifth Flash:
The Fakers Guide: no fifth flash means U11 (6821 PIA) is bad.

Techno Guide: Same test is performed on U11 as was performed on U10. See above.

Sixth Flash*:
The Fakers Guide: no sixth flash means either PIA U11 (6821) is bad, or U12 (555) timer is bad.

Techno Guide: The U9 CPU chip monitors PIA2, port CA1 (U11). If transitions from high to low are detected, the CPU decides the Display Interrupt Generator is working. If U12, a 555 timer, or any associated circuit component fails, the CPU will not flash the LED the sixth time.

* Note on Baby Pacman and Granny and the Gators, this flash step is skipped and not tested.

Seventh Flash**:
The Fakers Guide: no seventh flash means PIA U10 (6821) is bad, or there is no +43 volts DC for the solenoids (power transformer fuse F4 is probably blown), or U14 is bad.

Techno Guide: The U9 CPU chip monitors PIA1 port CB1 (U10). If transistion from high to low are detected, the CPU decides that the zero crossing detector is working. If U14 fails and the CB1 line is stuck high or low, the test will also fail. The zero crossing detector circuit input is the +43 volts DC line that is used for the solenoids. If the fuse in that line (F4 on the power transformer module) is blown when the game is turned on, the CPU will not flash the LED the seventh time.

** Note on Baby Pacman and Granny and the Gators this flash is the final flash. These games only had six flashes instead of seven.

Game Initialization.
The U9 CPU chip now initializes the two PIA's U10 and U11, assigning to each port its role as either an input or an output, as required. It then clears out U7 (6810 RAM). Now the CPU takes a picture of the settings of fixed switches S1 to S32 on the MPU board. It stores this "picture" in memory in chip U7. The CPU next jumps to a routine which turns on the "Game Over" feature light, lights the "Ball in Play" light, and the "Credit Indicator" light if there are credits stored in memory. It resets the drop targets and activates the saucer kickers or any kicker associated with a playfield device that can trap the ball and keep it out of the outhole. It then energizes the coin lockout solenoid to allow the game to accept coins (unless the credit maximum was met). Playfield and backbox feature lights associated with and appropriate to animation effects are turned on. With the game tested and initialized, the CPU now divides its time between monitoring momentary switches for closure (coin switch, credit button) and updating displays (lamps and score registers).

Problems/Solutions with the Seventh Flash.
If fuse F4 is blown on the solenoid board, the seventh flash will not occur. But what if there is a problem on the playfield which is forcing this fuse to blow (stopping the final LED flash on the MPU board, hence stopping your MPU diagnostics)?

The easiest way to deal with this is to remove the solenoid connectors from the solenoid driver board to the playfield. These connectors are on the left side of the solenoid driver board, and the one connector at the bottom right of the board too. This should allow the F4 fuse to be replaced, and the completion of the MPU booting process.

To help find the playfield coil that is causing the F4 fuse to blow, replace the connectors one at a time on the solenoid driver board (with the game off), and reboot the game. This will help issolate the bad coil.

Another thing to try: remove the under-the-playfield coil fuse, and replace fuse F4. If F4 does not blow, then one of the coils under the playfield is somehow shorted or staying energized (and blowing the solenoid driver F4 fuse). If fuse F4 still blows, there is either a problem with the backbox knocker, or the cabinet coin door lockout coil, the solenoid bridge rectifier (on the rectifier board), or the rectifier board's varister.

Also try removing connectors J1 and J3 from the rectifier board (this moves the solenoid power back a step further, not allowing it to get any further than the rectifier board). Replace fuse F4 on the solenoid driver board, and turn the game on. If the fuse still blows, the solenoid bridge rectifier (on the rectifier board) or the rectifier board's varister is probably at fault.

If it is a coil under the playfield, check the coils to see which one energizes when the game is powered on. Or disconnect a wire on each solenoid, and re-attach each wire, one at a time, until the fuse blows. At this point it could be the coil, coil diode, or coil driver transistor at fault.

Still No Seventh Flash - Other Things to Check.
First check TP3 and make sure there is 21 volts DC (of course this assumes fuse F4 is not blown on the solenoid board). If there is still no seventh flash, here are some other things to check. Remember all the components mentioned below are in the battery corrosion area.

• Check resistor R17 (150k). If this resistor goes open, or is not making good contact the circuit board, there will be no 7th flash. This resistor commonly fails.
• Check resistor R16 (2k).
• Check resistor R18 (1.5 meg).
• Check diodes CR52 and CR49 (1N4148 or 1N914).
If there is still no seventh flash, the last thing to check is chip U14 (4572).

MPU Boots Fine, but after Turning Off and Immediately back On, The MPU board is Locked.
Game is turned on and works fine. Then the game is turned off, and within a few minutes, turned back on. But the MPU board's LED is locked on, and will not (flicker) boot. The reset section of the MPU board has been rebuilt, as described in this document.

The first thing to suspect is MPU battery corrosion in the reset circuit. Inspect the board for any damage due to corrosion. The problem may be the reset line stays high from the battery power. When the battery is discharged enough, the game will restart. This can happen from the two 8.2k resistors (R1, R3) at the bottom of the MPU board. Other resistors in the reset section should be checked too (R2, R112, R120, R140, R139, R138, R140, R12, R11).

Seven Flashes Constantly Repeats.
The MPU boots and gets to the 7th flash, then start all over and repeats the seven flashes, then starts all over and does it over and over. This can happen from a bad 6810 RAM at U7. Or possibly a bad socket at U7.

---

3c. When things don't work: Game ROMs, EPROMs, and Jumpers - the Basics
Bally started using the improved -35 MPU board from 1979 to 1985. The later -35 MPU board can be used for ANY game from 1977 to 1985. The difference between the new -35 MPU and the early -17 MPU is mostly how the game ROMs are used and addressed (though the manufacturing and the type of sockets in the earlier -17 boards is also considered inferior to the -35 MPU boards). This section will address general concepts that are used on both the -17 and -35 (and -133) MPU boards.

Bally has provided us with about 35 different "jumper" locations on the -35 (and -133) MPU board, and about ten on the -17 MPU. This was done to handle all the different game ROM (read only memory) chip configuations, for all the different games. Depending on supply and demand for certain ROM chips, Bally pretty much had all the bases covered. They could use any combination of ROM types and sizes to fit their needs.

Important: Before you Change any Jumpers!!
It is EXTREMELY important that you have a working MPU board before you change any jumper locations! If you MPU board currently has ROMs in it, get it working first before you play with the jumpers. If you have your MPU board jumpered incorrectly for the game ROMs installed, the diagnostic LED light will stay on and the board will not power-up. So it is absolutely important that the jumpers are correct for the ROMs installed. Get your MPU board working first before proceeding.

Which MPU board Is It: -17 or -35 or -133? (How to Tell!)
Of course Bally silkscreen the MPU part number (AS-2518-17 or AS-2518-35 or AS-2518-133) right on the MPU board. But sometimes due to battery corrosion, etc, the part number can not be read. It is important to know which board is being worked on, as the game ROM/EPROM jumpers are different.

Basically there are two flavors of MPU board: the -17 or -35 (the -133 is really a -35 board with R113 changed to a diode CR52). The easiest way to tell which board is to examine connector J5. On a -17 MPU board, this connector will have 32 pins (including the removed "key" pin). On a -35/-133 MPU board, J5 will have 33 pins (including the removed "key" pin).

Bally/Williams' Jumper Information.
Though I personally don't recommend or use it, here is a link to the information that (recently) Williams posted about the original Bally board jumpers. You may find this information helpful (though personally I don't). It lives at ballyrm1.htm.

Masked ROMs versus EPROMs.
If you are repairing a game, you may be replacing the original masked (black) ROMs. These ROMs, as they get old, break very easily. In particular their pins tarnish and/or break off. The black tarnish is silver oxide, which is caused by oxygen and moisture in the air, and dis-similar metal electrolytic action between the silver plated pins and the tin plated sockets. The black oxide doesn't conduct well, and this can make the ROMs stop working correctly. They are not available any more, but they can be replaced with EPROMs.

EPROMs are basically the same as masked ROMs, but have a small cyrstal window on top of the chip. If UV (ultra-violet) light is shined through this window, the chip can be erased and re-programmed. An EPROM programmer is necessary to re-program an EPROM. These attach to your computer (though there are some stand alone ones too), and can "burn" a blank EPROM with a game's program code. After the EPROMs are burned, a sticker is placed over their window to prevent light from erasing them. EPROMs are the best replacement for your old and tired black masked ROMs.

Chances are if you are doing any repairs to a Bally MPU board, and you need new game ROMs, you will be installing EPROMs. EPROMs are available blank from many sources. But you need to have them "burned" first before you can use them.

The two chips on the left are the black "masked" ROMs. All masked ROMs used in these Bally games are known as "9316" EPROMs can be 2516, 2716, 2732, or 2532. The last two numbers identifies the size of the ROM (16k or 32k bits of program data). Masked ROMs are only usable in the game they were designed for. Note how their legs are tarnished black. The two chips on the right are EPROMs. Note the "window" which allows them to be erased, and re-programmed. Also note how the EPROM's legs are not tarnished. You can just read the notation on the one EPROM as "2532".

The Program Code that Lives inside the ROMs.
The memory inside each ROM or EPROM is the heart of your game. It contains the power-on diagnostics, the switch matrix, the game rules, and the coil assignments, among other things. Each model of pinball game has different program code that must be installed only in the game it is designed for. The program code is stored (burned) in your game's ROMs or EPROMs.

The Jumpers.
Each kind and size of ROM chip has its own set of enable and address requirements. To allow a board to use any type or size ROM that Bally had in stock, jumpers were used on the MPU board. It also provides a way to take a MPU board out of a newer game, and put it in an older game (and only have to change the jumpers and the game ROMs).

The wide array of jumpers Bally provides is very confusing. Some games use just one ROM at U6. Others use three ROMs at U6, U2, and U1. The size and type of these individual chips can change too.

What Type and Size are My ROM chips?
Before you can change a MPU board's jumpers to another game (or for new EPROMs), you need to know the type and size of chips you are installing. If you are installed Masked ROMs, these are all 9316 (16k bits of data) or 9332 (32k bits of data). If you are installing EPROMs, you need to read the markings on the EPROM. They will say what type and size of EPROM you have. They will be 2516, 2716 (both 2516 and 2716 are the same type of 16k bit EPROM), 2532, or 2732 (32k bit EPROMs). Note the jumpers for 2532 and 2732 EPROMs are different, as these chips have different pin assignment (but the jumpers for 2532 EPROMs and 9332 ROMs are the same, which is the ONLY sharing of masked ROM and EPROM jumpers). This is unlike 2516 EPROMs and 2716 EPROMs, which are identical and have identical jumpers.

What if I don't have an EPROM Programmer?
You can also buy the above EPROM chips already programmed in 2732 format (or any other size) from Flipperwinkel.nl

Using 2532 EPROMs instead of 9332 Masked ROMs.
If the game in question is a later Bally game with 9332 masked ROMs, these can be changed to 2532 EPROMs with NO jumper modifications! This can be handy and convenient if the original black 9332 masked ROMs need changing, but the repair person doesn't want to mess with the jumpers.

What Do the Masked ROMs Chip Numbers Mean?
If the game in question uses original black masked ROMs, there are numbers on the ROMs that denote information about the chip. This information is can be seen by clicking ballyro2.htm, where the ROM numbers are sort numerically. Another page located at ballyrom.htm shows the same information, but sorted by game name. Also shown are the original jumper settings.

Note the higher -xx number means a later revision. In the case of the U6 chips, that revision is important, as generally a game can not be run with the "wrong" U6 part. But for the U1/U2 chips, it usually means a later version of the same game (and all the chips must be of the "correct" revision to match the others, though there's not always a good way to know what that is).

As an example, Lost World uses "720-28" for U6. But then the other chips should all be "729-xx", with the latest revision being "729-33" at U1, and "729-48" at U2. If the game has an earlier version, they would have some other numbers after "729-". But note there can be no mixing of old and new versions!

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* Go to the Bally Repair Guide Part 1
* Go to the Bally Repair Guide Part 3